1. Field of the Invention
The present invention relates to a copper alloy with high strength and high electroconductivity and excellent in bending workability also, and relates more specifically to a copper alloy suitable to materials for various electric and electronic parts used for a connector, lead frame, relay, switch, wiring, terminal and the like constituting electric and electronic parts.
2. Description of the Related Art
In recent years, associated with requirements of miniaturization and weight reduction of electronic apparatuses, electric systems of electric and electronic parts have been more complicated and highly integrated, and characteristics capable of standing thinning and working of a complicated shape are required for materials for various electric and electronic parts.
For example, with respect to the materials for various electric and electronic parts used for current-carrying parts such as a connector, lead frame, relay, switch and the like constituting electric and electronic parts, the cross-sectional area of the material receiving a same load reduces and the cross-sectional area of the material relative to the current-carrying amount also reduces by miniaturization and thinning, therefore excellent electroconductivity is required in order to suppress generation of Joule heat by current-carrying, and high strength capable of standing the stress imparted in assembling and operating electric and electronic apparatuses and bending workability that does not cause breakage and the like even when the electric and electronic parts are bent have been required.
Although a Cu—Fe—P alloy has been used commonly as a material for electric and electronic parts, when an alloy composition such as Sn and the like was added in order to increase the strength, electroconductivity deteriorated and it was difficult to balance the strength and electroconductivity (strength-conductivity balance).
Also, though an alloy of a precipitation hardening type (Cu—Ni—Si alloy) has been proposed as a high strength material, when the content of Ni and Si was reduced in order to improve electroconductivity, the tensile strength dropped, and therefore it was difficult to secure the strength-electroconductivity balance.
As a material superior in the strength-electroconductivity balance compared with conventional Cu—Fe—P alloy and Cu—Ni—Si alloy, a Cu—Cr-based alloy has been proposed (Japanese Unexamined Patent Application Publication No. 2005-29857). However, coarse precipitates were formed in hot rolling, and there was a limit both in increasing the strength and in increasing the electroconductivity.
Also, as a copper alloy excellent in the strength-electroconductivity balance and the workability, a Cu—Cr—Sn-based alloy has been proposed (Japanese Unexamined Patent Application Publication No. H6-081090). However, in the Cu—Cr—Sn-based alloy, a solution heat treatment at high temperature was required, and there were such problems in production that the production process became complicated and the like.
Further, as a copper alloy excellent in strength, electroconductivity and high temperature strength, a Cu—Cr—Ti—Zr alloy has been proposed (Japanese Patent No. 3731600). However, in this copper alloy, the strength and electroconductivity could be improved, but bending workability could not be improved sufficiently.
Also, as a copper alloy excellent in the strength-electroconductivity balance, a Cu—Cr—Ti—Si alloy has been proposed (Japanese Patent No. 2515127). According to this Japanese Patent No. 2515127, consideration was paid for bending workability also, however the copper alloy was not sufficient with respect to bending workability that was severe as described below.
Accompanying weight reduction, miniaturization and the like of electric and electronic apparatuses in recent years, working more complicated than before is executed for materials for electric and electronic parts such as subjecting a material thinned to bending work, executing bending work after subjecting wiring to notching (notching work) into fine width, and the like, therefore requirements not only for improvement of the strength but also for bending workability have become further higher, and a material excellent not only in the strength-electroconductivity balance but also in the strength-bending workability balance has been required.